import datetime
import logging
import math
import time
import torch
import os
import tarfile
from os import path as osp

from pyiqa.data import build_dataloader, build_dataset
from pyiqa.data.data_sampler import EnlargedSampler
from pyiqa.data.prefetch_dataloader import CPUPrefetcher, CUDAPrefetcher
from pyiqa.models import build_model
from pyiqa.utils import (
    AvgTimer,
    MessageLogger,
    check_resume,
    get_env_info,
    get_root_logger,
    get_time_str,
    init_tb_logger,
    init_wandb_logger,
    make_exp_dirs,
    mkdir_and_rename,
    scandir,
    load_file_from_url,
)
from pyiqa.utils.options import copy_opt_file, dict2str, parse_options
from pyiqa.utils.dist_util import master_only


@master_only
def init_tb_loggers(opt):
    # initialize wandb logger before tensorboard logger to allow proper sync
    if (
        (opt['logger'].get('wandb') is not None)
        and (opt['logger']['wandb'].get('project') is not None)
        and ('debug' not in opt['name'])
    ):
        assert opt['logger'].get('use_tb_logger') is True, (
            'should turn on tensorboard when using wandb'
        )
        init_wandb_logger(opt)
    tb_logger = None
    if opt['logger'].get('use_tb_logger') and 'debug' not in opt['name']:
        tb_logger = init_tb_logger(
            log_dir=osp.join(opt['root_path'], 'tb_logger', opt['name'])
        )
    return tb_logger


def create_train_val_dataloader(opt, logger):
    # create train and val dataloaders
    train_loader, val_loaders = None, []
    for phase, dataset_opt in opt['datasets'].items():
        if phase == 'train':
            dataset_enlarge_ratio = dataset_opt.get('dataset_enlarge_ratio', 1)
            train_set = build_dataset(dataset_opt)
            train_sampler = EnlargedSampler(
                train_set,
                opt['world_size'],
                opt['rank'],
                dataset_enlarge_ratio,
                dataset_opt.get('use_shuffle', True),
            )
            train_loader = build_dataloader(
                train_set,
                dataset_opt,
                num_gpu=opt['num_gpu'],
                dist=opt['dist'],
                sampler=train_sampler,
                seed=opt['manual_seed'],
            )

            num_iter_per_epoch = math.ceil(
                len(train_set)
                * dataset_enlarge_ratio
                / (dataset_opt['batch_size_per_gpu'] * opt['world_size'])
            )

            total_epochs = opt['train'].get('total_epoch', None)
            if total_epochs is not None:
                total_epochs = int(total_epochs)
                total_iters = total_epochs * (num_iter_per_epoch)
                opt['train']['total_iter'] = total_iters
            else:
                total_iters = int(opt['train']['total_iter'])
                total_epochs = math.ceil(total_iters / (num_iter_per_epoch))

            logger.info(
                'Training statistics:'
                f'\n\tNumber of train images: {len(train_set)}'
                f'\n\tDataset enlarge ratio: {dataset_enlarge_ratio}'
                f'\n\tBatch size per gpu: {dataset_opt["batch_size_per_gpu"]}'
                f'\n\tWorld size (gpu number): {opt["world_size"]}'
                f'\n\tRequire iter number per epoch: {num_iter_per_epoch}'
                f'\n\tTotal epochs: {total_epochs}; iters: {total_iters}.'
            )
        elif phase.split('_')[0] == 'val':
            val_set = build_dataset(dataset_opt)
            val_loader = build_dataloader(
                val_set,
                dataset_opt,
                num_gpu=opt['num_gpu'],
                dist=opt['dist'],
                sampler=None,
                seed=opt['manual_seed'],
            )
            logger.info(
                f'Number of val images/folders in {dataset_opt["name"]}: {len(val_set)}'
            )
            val_loaders.append(val_loader)
        else:
            raise ValueError(f'Dataset phase {phase} is not recognized.')

    return train_loader, train_sampler, val_loaders, total_epochs, total_iters


def load_resume_state(opt):
    resume_state_path = None
    if opt['auto_resume']:
        state_path = osp.join('experiments', opt['name'], 'training_states')
        if osp.isdir(state_path):
            states = list(
                scandir(state_path, suffix='state', recursive=False, full_path=False)
            )
            if len(states) != 0:
                states = [float(v.split('.state')[0]) for v in states]
                resume_state_path = osp.join(state_path, f'{max(states):.0f}.state')
                opt['path']['resume_state'] = resume_state_path
    else:
        if opt['path'].get('resume_state'):
            resume_state_path = opt['path']['resume_state']

    if resume_state_path is None:
        resume_state = None
    else:
        device_id = torch.cuda.current_device()
        resume_state = torch.load(
            resume_state_path, map_location=lambda storage, loc: storage.cuda(device_id)
        )
        check_resume(opt, resume_state['iter'])
    return resume_state


def train_pipeline(root_path, opt=None, args=None):
    # parse options, set distributed setting, set random seed
    if opt is None and args is None:
        opt, args = parse_options(root_path, is_train=True)
    opt['root_path'] = root_path

    torch.backends.cudnn.benchmark = True
    # torch.backends.cudnn.deterministic = True

    # load resume states if necessary
    resume_state = load_resume_state(opt)
    # mkdir for experiments and logger
    if resume_state is None:
        make_exp_dirs(opt)
        if (
            opt['logger'].get('use_tb_logger')
            and 'debug' not in opt['name']
            and opt['rank'] == 0
        ):
            os.makedirs(osp.join(opt['root_path'], 'tb_logger_archived'), exist_ok=True)
            mkdir_and_rename(osp.join(opt['root_path'], 'tb_logger', opt['name']))

    # copy the yml file to the experiment root
    copy_opt_file(args.opt, opt['path']['experiments_root'])

    # WARNING: should not use get_root_logger in the above codes, including the called functions
    # Otherwise the logger will not be properly initialized
    log_file = osp.join(opt['path']['log'], f'train_{opt["name"]}_{get_time_str()}.log')
    logger = get_root_logger(
        logger_name='pyiqa', log_level=logging.INFO, log_file=log_file
    )
    logger.info(get_env_info())
    logger.info(dict2str(opt))
    # initialize wandb and tb loggers
    tb_logger = init_tb_loggers(opt)

    # create train and validation dataloaders
    result = create_train_val_dataloader(opt, logger)
    train_loader, train_sampler, val_loaders, total_epochs, total_iters = result

    # create model
    model = build_model(opt)
    if resume_state:  # resume training
        model.resume_training(resume_state)  # handle optimizers and schedulers
        logger.info(
            f'Resuming training from epoch: {resume_state["epoch"]}, '
            f'iter: {resume_state["iter"]}.'
        )
        start_epoch = resume_state['epoch']
        current_iter = resume_state['iter']
    else:
        start_epoch = 0
        current_iter = 0

    # create message logger (formatted outputs)
    msg_logger = MessageLogger(opt, current_iter, tb_logger)

    # dataloader prefetcher
    prefetch_mode = opt['datasets']['train'].get('prefetch_mode')
    if prefetch_mode is None or prefetch_mode == 'cpu':
        prefetcher = CPUPrefetcher(train_loader)
    elif prefetch_mode == 'cuda':
        prefetcher = CUDAPrefetcher(train_loader, opt)
        logger.info(f'Use {prefetch_mode} prefetch dataloader')
        if opt['datasets']['train'].get('pin_memory') is not True:
            raise ValueError('Please set pin_memory=True for CUDAPrefetcher.')
    else:
        raise ValueError(
            f'Wrong prefetch_mode {prefetch_mode}.'
            "Supported ones are: None, 'cuda', 'cpu'."
        )

    # training
    logger.info(f'Start training from epoch: {start_epoch}, iter: {current_iter}')
    data_timer, iter_timer = AvgTimer(), AvgTimer()
    start_time = time.time()

    for epoch in range(start_epoch, total_epochs + 1):
        train_sampler.set_epoch(epoch)
        prefetcher.reset()
        train_data = prefetcher.next()

        while train_data is not None:
            data_timer.record()

            current_iter += 1
            if current_iter > total_iters:
                break
            # update learning rate
            # model.update_learning_rate(current_iter, warmup_iter=opt['train'].get('warmup_iter', -1))
            # training
            model.feed_data(train_data)
            model.optimize_parameters(current_iter)
            iter_timer.record()
            if current_iter == 1:
                # reset start time in msg_logger for more accurate eta_time
                # not work in resume mode
                msg_logger.reset_start_time()
            # log
            if current_iter % opt['logger']['print_freq'] == 0:
                log_vars = {'epoch': epoch, 'iter': current_iter}
                log_vars.update({'lrs': model.get_current_learning_rate()})
                log_vars.update(
                    {
                        'time': iter_timer.get_avg_time(),
                        'data_time': data_timer.get_avg_time(),
                    }
                )
                log_vars.update(model.get_current_log())
                msg_logger(log_vars)

            # log images
            log_img_freq = opt['logger'].get('log_imgs_freq', 1e99)
            if current_iter % log_img_freq == 0:
                visual_imgs = model.get_current_visuals()
                if tb_logger and visual_imgs is not None:
                    for k, v in visual_imgs.items():
                        tb_logger.add_images(
                            f'ckpt_imgs/{k}', v.clamp(0, 1), current_iter
                        )

            # save models and training states
            save_ckpt_freq = opt['logger'].get('save_checkpoint_freq', 9e9)
            if current_iter % save_ckpt_freq == 0:
                logger.info('Saving models and training states.')
                model.save(epoch, current_iter)

            if current_iter % opt['logger']['save_latest_freq'] == 0:
                logger.info('Saving latest models and training states.')
                model.save(epoch, -1)

            # validation
            if opt.get('val') is not None and (
                current_iter % opt['val']['val_freq'] == 0
            ):
                logger.info(
                    f'{len(val_loaders)} validation datasets are used for validation.'
                )
                for val_loader in val_loaders:
                    model.validation(
                        val_loader, current_iter, tb_logger, opt['val']['save_img']
                    )

            data_timer.start()
            iter_timer.start()
            train_data = prefetcher.next()

            if 'debug' in opt['name'] and current_iter >= 8:
                break
        # end of iter
        # use epoch based learning rate scheduler
        model.update_learning_rate(
            epoch + 2, warmup_iter=opt['train'].get('warmup_iter', -1)
        )

        if 'debug' in opt['name'] and epoch >= 2:
            break
    # end of epoch

    consumed_time = str(datetime.timedelta(seconds=int(time.time() - start_time)))
    logger.info(f'End of training. Time consumed: {consumed_time}')
    logger.info('Save the latest model.')
    model.save(epoch=-1, current_iter=-1)  # -1 stands for the latest
    if opt.get('val') is not None:
        for val_loader in val_loaders:
            model.validation(
                val_loader, current_iter, tb_logger, opt['val']['save_img']
            )
    if tb_logger:
        tb_logger.close()

    if opt['rank'] == 0:
        return model.best_metric_results


if __name__ == '__main__':
    root_path = osp.abspath(osp.join(__file__, osp.pardir, osp.pardir))
    train_pipeline(root_path)
